1. Field of the Invention
The invention relates to the esterification of rosin and in particular relates to the esterification of tall oil rosins with polyhydric alcohols.
2. Brief Description of the Prior Art
Tall oil rosin, obtained upon the distillation of tall oil or tall oil fractions, is esterified with pentaerythritol. The esters are useful as tackifiers in various adhesive formulations and also can be used as intermediates for a variety of valuable products including coating and ink resins. The esters prepared normally possess an objectionable dark color and a typical tall oil rosin odor.
The U.S. Pat. No. 3,780,013 describes a method of improving the color of the pentaerythritol esters of tall oil rosin by the incremental addition of a phenol sulfide to the esterification reaction mixture.
The U.S. Pat. No. 3,780,012 describes a process of improving the color of tall oil esters of pentaerythritol by pretreating the rosin with paraformaldehyde under certain conditions and distilling the treated rosin.
We have found that esters of tall oil rosin and pentaerythritol having an improved, lighter color can be obtained by carrying out the esterification in the presence of activated carbon. Unlike prior art processes such as described above, the decolorizing agent may easily be removed from the product by simple filtration. The process is economical and easy to carry out.
Activated carbon has long been known to remove color bodies and odor from organic material. The uniqueness of the present invention is the significant improvement observed when carbon is included during the reaction as opposed to carbon treatment of the rosin prior to esterification or post treatment.